EP0587341 describes a high temperature corrosion resistant composite coating where the process includes the following steps:
Applying an alloy coating material of the MCrAlY type.
Optionally chromizing the MCrAlY type coating to produce a coating with a chromized top layer having extra chromium in solid solution in the M constituent of the coating.
Aluminizing the coating to produce a coating having a surface layer containing aluminides of the M constituent of the coating.
Depositing a platinum layer on top of the surface of the aluminized coating.
EP 1327702 describes a MCrAlY coating system comprising an inner layer of beta-NiAl and an outer layer of gamma/beta-MCrAlY and TBC. In the document it is stated that the oxidation resistance can be improved for theses layers of coating by adding 0.1-4% Si. The coatings are deposited using a gas phase method, CVD, PVD etc.
US 2005/0003227 describes a similar system as in US '227, but here is also an intermediate layer of a platinum type of metal included. In the document it is stated that the oxidation resistance can be improved for these layers of coating by adding 0.1-4% Si.
EP 1029100/U.S. Pat. No. 6,416,882 describes a MCrAlY type of bond coat comprising up to 2% silicon.
Aluminide and/or chromium modified coating systems are also described in U.S. Pat. No. 7,229,701, U.S. Pat. No. 6,183,888, U.S. Pat. No. 7,060,366, U.S. Pat. No. 6,287,644, EP 1 082 216, U.S. Pat. No. 6,001,492, U.S. Pat. No. 5,507,623, EP 1 541 808 and U.S. Pat. No. 6,569,492.
EP 0587341 describes a high temperature corrosion resistant composite coating where the process includes the following steps:
Applying an alloy coating material of the MCrAlY type.
Optionally chromizing the MCrAlY type coating to produce a coating with a chromized top layer having extra chromium in solid solution in the M constituent of the coating.
Aluminizing the coating to produce a coating having a surface layer containing aluminides of the M constituent of the coating.
Depositing a platinum layer on top of the surface of the aluminized coating.
But these coatings are still not good enough.